Final (Part 3) Flashcards
3 mechanisms of speciation?
Ecological, Polyploidization, Reinforcement
end point of taxa?
reaches irreversible endpoint when two taxa cannot form fertile hybrids, seperate gene pools between alleles cannot move
what is a biological species
groups that actually or potentially interbreed and produce fertile offspring, and dont form offspring with members of other groups
what is speciation
process by which one species splits into two or more species
what are the results of experimental evolution
predicts stronger behavioural isolation between populations adapted to different environments compared to populations adapted to same
environment
geography of speciation?
Sympatric vs. allopatric are two extremes in a gradient of gene flow between diverging populations
dis/advantages of BSC
Provides a straightforward approach to studying speciation
*Can’t be applied to asexual taxa (e.g., prokaryotes) or fossils
*Can be hard to assay reproductive barriers
prezygotic barriers?
Lower likelihood of success when mating- habitat isolation, temporal isolation, behavioral/pollinator isolation, mechanical isolation or gametic isolation
postzygotic barriers?
reduce survival of hybrid- genetic incompatibilites, ecologically-dependent postzygotic isolation (fall between niches),
what is polyploidization
increase in the # of whole sets of chromosomes (i.e., 2n, 3n, 4n, etc.)
postzygotic can be instantaneous
occurs in sympatry, common in ferns & flowering plants
what is BSC
biological species concept
new daughter species…
share characteristics because they are descended from common ancestor, related to one another through varying degrees
how to study speciation in nature?
Hybrids struggle in mismatched environments due to their traits. Ecological differences drive distinct traits in species, tested by transplant experiments.
Ecological SC
defines species based on their ecological niche; i.e., groups that inhabit thesame niche
is sympatric speciation common?
Evidence suggests sympatric speciation is extremely rare
what is ecological speciation?
reproductive isolation arises as a by-product of adaptation to different environments or niches
* can occur under any geographic context
experimental evolution?
technique in which multiple, replicate populations
are derived from a common ancestor and then their evolution is tracked under conditions that the experimenter controls
what is reinforcement
The strengthening of prezygotic barrier by natural selection in response to reduced
hybrid fitness
Can complete a speciation event initiated by any mechanism, Requires contact
Morphological SC
defines species based on morphological similarity
2 ways to study speciation
labratory studies, speciation in nature
example of ecological speciation
Darwin finches, adapting different beaks to different food sources on various islands
what is reproductive isolation
opposite of compatability, result of reproductive barriers
2 types of polyploidization
autopolyploid - an individual with more than two
chromosome sets derived from a single species
allopolyploid - an individual with more than two
chromosome sets derived from different species
allopatric vs sympatric geography
Allopatric – occurring in separate, non-overlapping geographic areas
Sympatric – occurring in the same, overlapping geographic area
example of reinforcement
closely related butterfly species occasionally interbreed, natural selection favors distinct traits such as unique colors or behaviors that reduce successful mating between them
